Hajime Kawahara

Last updated: Sep 10, 2013 at 15:39
Hajime Kawahara
The University of Tokyo
Job title
Assistant Professor
Research funding number


I am currently working on characterization of exoplanets.

Research Areas


Awards & Honors

Jan 2012
Martin and Beate Block Award, Aspen center for physics

Published Papers

Hajime Kawahara, Teruyuki Hirano, Kenji Kurosaki, Yuichi Ito, Masahiro Ikoma
accepted by ApJL      Sep 2013   [Refereed]
Hajime Kawahara
ApJ Letters   760(1) L13   Nov 2012   [Refereed]
Hajime Kawahara, Taro Matsuo, Michihiro Takami, Yuka Fujii, Takayuki Kotani, Naoshi Murakami, Motohide Tamura, Olivier Guyon
Astrophysical Journal   758(1) 13   Oct 2012   [Refereed]
The oxygen absorption line imprinted in the scattered light from the Earth- like planets has been considered the most promising metabolic biomarker of the exo-life. We examine the feasibility of the detection of the 1.27 μm oxygen band from habita...
Hiroki Akamatsu, Hajime Kawahara
Accepted by PASJ      Sep 2012   [Refereed]
We perform a systematic X-ray analysis of six giant radio relics of four
clusters with Suzaku satellite by compiling new analysis of CIZA 2242.8-5301,
Zwcl 2341.1-0000, and Abell 3667 and previous results of A3667 and A3376.
Especially we first ob...
Yuka Fujii, Hajime Kawahara
Astrophysical Journal   755 101   Aug 2012   [Refereed]
Aiming at obtaining detailed information of surface environment of
Earth-analogs, Kawahara & Fujii 2011 proposed an inversion technique of annual
scattered light curves named the spin-orbit tomography (SOT), which enables one
to sketch a 2-dimensi...
Mark Swain, Pieter Deroo, Giovanna Tinetti, Morgan Hollis, Marcell Tessenyi, Michael Line, Hajime Kawahara, Yuka Fujii, Adam Showman, Sergey Yurchenko
   May 2012
We report near-infrared measurements of the terminator region transmission
spectrum and dayside emission spectrum of the exoplanet WASP-12b obtained using
the HST WFC3 instrument. The disk-average dayside brightness temperature
averages about 2900...
Hajime Kawahara, Yuka Fujii
ApJ Letters   739(2) L62   Sep 2011   [Refereed]
We develop an inversion technique of annual scattered light curves to sketch a two-dimensional albedo map of exoplanets in face-on orbits. As a test bed for future observations of extrasolar terrestrial planets, we apply this mapping technique to ...
Yuka Fujii, Hajime Kawahara, Yasushi Suto, Satoru Fukuda, Teruyuki Nakajima, Timothy A. Livengood, Edwin L. Turner
ApJ   738 184   Aug 2011   [Refereed]
As a test-bed for future investigations of directly imaged terrestrial
exoplanets, we present the recovery of the surface components of the Earth from
multi-band diurnal light curves obtained with the EPOXI spacecraft. We find
that the presence an...
Yoh Takei, Eugenio Ursino, Enzo Branchini, Takaya Ohashi, Hajime Kawahara, Kazuhisa Mitsuda, Luigi Piro, Alessandra Corsi, Lorenzo Amati, Jan-Willem den Herder, Massimiliano Galeazzi, Jelle Kaastra, Lauro Moscardini, Fabrizio Nicastro, Frits Paerels, Mauro Roncarelli, Matteo Viel
ApJ   734(2) 91   Jun 2011   [Refereed]
We assess the possibility to detect the warm-hot intergalactic medium (WHIM)
in emission and to characterize its physical conditions and spatial
distribution through spatially resolved X-ray spectroscopy, in the framework of
the recently proposed ...
Thierry Sousbie, Christophe Pichon, Hajime Kawahara
MNRAS   414(1) 384-403   Jun 2011   [Refereed]
The recently introduced discrete persistent structure extractor (DisPerSE,
Soubie 2010, paper I) is implemented on realistic 3D cosmological simulations
and observed redshift catalogues (SDSS); it is found that DisPerSE traces
equally well the obs...
Hajime Kawahara, Hiroshi Yoshitake, Takahiro Nishimichi, Thierry Sousbie
ApJ Letters   727 L38   Jan 2011   [Refereed]
We report on a new merging group of galaxies, Suzaku J1552+2739 at z ~ 0.08
revealed by a SUZAKU observation. The group was found by observing a junction
of galaxy filaments optically identified in the Sloan Digital Sky Survey
spectroscopic data. ...
Hajime Kawahara, Yuka Fujii
ApJ   720(2) 1333-1350   Aug 2010   [Refereed]
Scattered lights from terrestrial exoplanets provide valuable information
about the planetary surface. Applying the surface reconstruction method
proposed by Fujii et al. (2010) to both diurnal and annual variations of the
scattered light, we deve...
Erik D. Reese, Hajime Kawahara, Tetsu Kitayama, Naomi Ota, Shin Sasaki, Yasushi Suto
ApJ   721(1) 653   Aug 2010   [Refereed]
We perform a uniform, systematic analysis of a sample of 38 X-ray galaxy
clusters with three different Chandra calibrations. The temperatures change
systematically between calibrations. Cluster temperatures change on average by
roughly ~6% for the...
Hajime Kawahara
ApJ   719(2) 1926-1931   Aug 2010   [Refereed]
We derive the axis ratio distribution of X-ray clusters using the XMM-Newton
catalogue (Snowden et al. 2008). By fitting the contour lines of the X-ray
image by ellipses, we confirm the X-ray distribution is well approximated by
the elliptic distr...
Y. Fujii, H. Kawahara, Y. Suto, A. Taruya, S. Fukuda, T. Nakajima, E. L. Turner
ApJ   715(2) 866-880   Jun 2010   [Refereed]
Characterizing the surfaces of rocky exoplanets via the scattered light will
be an essential challenge to investigate the existence of life on habitable
exoplanets. We present a simple reconstruction method for fractional areas of
different surfac...
Hajime Kawahara, Erik D. Reese, Tetsu Kitayama, Shin Sasaki, Yasushi Suto
ApJ   687(2) 936-950   Nov 2008   [Refereed]
Our previous analysis indicates that small-scale fluctuations in the
intracluster medium (ICM) from cosmological hydrodynamic simulations follow the
lognormal distribution. In order to test the lognormal nature of the ICM
directly against X-ray ob...
Hajime Kawahara, Tetsu Kitayama, Shin Sasaki, Yasushi Suto
ApJ   674(1) 11-21   Feb 2008   [Refereed]
The Hubble constant estimated from the combined analysis of the
Sunyaev-Zel'dovich effect and X-ray observations of galaxy clusters is
systematically lower than those from other methods by 10-15 percent. We examine
the origin of the systematic und...
Kosuke Sato, Noriko Y. Yamasaki, Manabu Ishida, Yoshitaka Ishisaki, Takaya Ohashi, Hajime Kawahara, Takao Kitaguchi, Madoka Kawaharada, Motohide Kokubun, Kazuo Makishima, Naomi Ota, Kazuhiro Nakazawa, Takayuki Tamura, Kyoko Matsushita, Naomi Kawano, Yasushi Fukazawa, John P. Hughes
PASJ   59(2) 299-317   Apr 2007   [Refereed]
We carried out observations of the central and 20' east offset regions of the
cluster of galaxies Abell 1060 with Suzaku. Spatially resolved X-ray spectral
analysis has revealed temperature and abundance profiles of Abell 1060 out to
27' ~ 380; /h...
Hajime Kawahara, Yasushi Suto, Tetsu Kitayama, Shin Sasaki, Mamoru Shimizu, Elena Rasia, Klaus Dolag
ApJ   659(1) 257-266   Apr 2007   [Refereed]
The origin of the recently reported systematic bias in the spectroscopic
temperature of galaxy clusters is investigated using cosmological
hydrodynamical simulations. We find that the local inhomogeneities of the gas
temperature and density, after...
Hajime Kawahara, Kohji Yoshikawa, Shin Sasaki, Yasushi Suto, Nobuyuki Kawai, Kazuhisa Mitsuda, Takaya Ohashi, Noriko Yamasaki
PASJ   58(4) 657-671   Aug 2006   [Refereed]
We discuss the detectability of Warm/Hot Intergalactic medium (WHIM) via the
absorption lines toward bright point sources with a future X-ray satellite
mission, XEUS. While we consider bright QSOs as specific examples, the
methodology can be appli...

Academic & Professional Experience

Nov 2012
Assistant Professor, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo
Apr 2010
Oct 2012
JSPS/PD (Tokyo Metropolitan University)
Apr 2009
Mar 2010
JSPS/PD (The University of Tokyo)